B‑1366

MANAGING INSECT AND MITE PESTS

OF TEXAS CORN

Patrick Porter, Gregory B. Cronholm, Roy D. Parker,

Noel Troxclair, Carl D. Patrick, Pat Morrison, and Thomas L. Archer*

2001

 

 

 

*Respectively, Extension entomologist at Lubbock; Extension agent‑pest management at Plainview; Extension entomologist at Corpus Christi; Extension entomologist at Uvalde; Extension entomologist at Amarillo; Associate Department Head, Department of Entomology; Professor of Entomology, Texas Agricultural Experiment Station at Lubbock.

 

Table of Contents

 

Introduction

Policy Statement for Making Pest Management Suggestions

Endangered Species Regulations

Worker Protection Standard

Biological Control

Transgenic Corn

 

Pre-Emergence Insect Control

Seedling to Tassel Stage Insect Control

 

Tassel to Hard Dough Stage Insect Control

 

Insecticide Application Methods

Protecting Bees and Other Pollinators from Insecticides

APPENDIX i iNSECT AND mITE pESTS  

Appendix II Beneficial Arthropods

 

Introduction

Corn is subject to insect attack throughout the growing season. Despite natural predators and parasites, some insects may reach damaging levels and may require chemical control. However, plant damage is not always directly related to insect numbers. Other factors such as plant vigor, growth stage, moisture conditions, time of year, parasite and predator abundance and crop rotation are equally important. Therefore, chemical treatments should be based on careful evaluation of economic and natural control factors.


The wise use of insecticides requires that producers inspect their crops frequently to determine if damaging numbers of insect or mite pests are present. This publication provides methods for determining insect numbers and guides for determining the need for pesticides. Because seed production corn and sweet corn are more susceptible to insect damage and are also more economically valuable than field corn, producers may need to control pests in seed and sweet corn even when fewer pests are present. Recommendations in this bulletin primarily refer to insect and mite control on field corn.

A few insect and mite pests attacking corn in Texas show resistance to pesticides that once were effective. Generally, the more extensively a pesticide is used, the more rapidly resistance develops. Therefore, pesticides should be used only when needed. The actual need can be determined only by frequent inspections of the crop to determine pest numbers.

 

This guide discusses insect and mite pests in the approximate seasonal order that they damage corn - pre‑emergence, seedling to tassel and tassel to hard dough.

 

 

Policy Statement for Making Suggestions

This is not a complete listing of all products registered for corn and does not list all uses of products mentioned. The insecticides and their suggested use patterns included in this publication reflect a consensus of Extension and Research  entomologists based on field tests. The data from these field tests met the minimum requirements outlined in the Guidelines for the Annual Entomology Research Review and Extension Guide Revision Conference. Products listed must conform to its performance standards and avoid undue environmental consequences.

Suggested insecticide use rates have shown sufficient effectiveness in tests to provide adequate control in field situations. However, it is impossible to eliminate all risks. Unforeseen or unexpected conditions or circumstances may result in less than satisfactory results. Texas Cooperative Extension  will not assume responsibility for such risks. Such responsibility shall be assumed by the user of this publication.

Suggested pesticides must be registered and labeled by the Environmental Protection Agency and the Texas Department of Agriculture. The status of pesticide label clearances is subject to change and may have changed since this publication was printed.

The USER is always responsible for the effects of pesticide residues on his livestock and crops, as well as for problems that could arise from drift or movement of the pesticide. Always read and follow carefully the instructions on the container label. Pay particular attention to practices that ensure worker safety.                          

For additional information, contact your county Extension staff; write the Extension Entomologist, 2475 TAMU, Texas A&M University, College Station, TX 77843‑2475; or call (979) 845‑7026.

 

 

Endangered Species Regulations

The Endangered Species Act was enacted to protect and to assist in the recovery of animals and plants that are in danger of becoming extinct. In response to the Endangered Species Act, many pesticide labels now carry restrictions limiting the use of products or application methods in areas designated as biologically sensitive. These restrictions are subject to change. Refer to the Environmental Hazards or Endangered Species discussion sections of product labels and/or call your local county Extension agent or Fish and Wildlife Service personnel to determine what restrictions apply to your area. Regardless of the law, pesticide users can be good neighbors by being aware of how their actions may affect people and the environment.

 

 

Worker Protection Standard

The Worker Protection Standard (WPS) is a set of federal regulations that applies to producers who employ people to produce a plant or plant product for sale. The WPS affects workers who will apply pesticides (agricultural handlers) or work in an area where pesticides have been applied (agricultural workers). Since 1995, if you are using a pesticide product with labeling that refers to the Worker Protection Standard, you must comply with it. The WPS requires that you provide three basic types of pesticide protection to your employees. You must:

 

$                   Inform employees about possible exposure

$                   Protect employees from exposure and,

$                   Mitigate pesticide exposures that employees might receive.

 

All agricultural pesticides bear a WPS statement in the "DIRECTIONS FOR USE" part of the label. For more detailed information, consult EPA publication 735‑B‑93‑001 The Worker Protection Standard for Agricultural Pesticides ‑‑ How to Comply: What Employers Need to Know (GPO #055‑000‑0442‑1), or call Texas Department of Agriculture, Pesticide Worker Protection Program, (512) 463‑7717.

 

 

Biological Control

Biological control is the use of living organisms, such as parasites, predators and disease, to control pests. Organisms that control pests are called natural enemies. In corn, natural enemies include minute pirate bugs, spiders, lady beetles, predatory mites and thrips, and a variety of tiny wasps that parasitize insect pests. In addition, weather and inadequate food often hold insect and mite populations below damaging levels. It is important to recognize the effects of these natural control factors and, where possible, encourage their action.

Biological control includes the conservation, augmentation and importation of natural enemies. A producer can conserve existing populations of natural enemies by minimizing insecticide applications and using insecticides that are more toxic to the target pest than to the natural enemy. Augmentation involves purchasing and releasing specimens of the natural enemies. Classical biological control - the third type - involves importing natural enemies from other countries.

 

 

Transgenic Corn

Transgenic corn produces some of the insecticidal endotoxins (poisons) found in the bacterium Bacillus thuringiensis (Bt). These proteins are highly toxic to certain insect pests but have little or no effect on humans, livestock, most beneficial insects and other nontarget organisms.  Because planting Bt corn reduces the need for insecticides, there is less human and environmental exposure to insecticides, and the producer has lower production costs.    

Extensive field testing indicates that Bt corn hybrids provide excellent control of first and usually second generation European corn borers, southwestern corn borers and sugarcane borers. Bt corn varieties also may be effective in controlling or suppressing some other lepidopterous (caterpillar) pests, including corn earworm. There are significant differences among the types of Bt corn and their ability to control such pests.

 

The presence of Bt does not enhance yield; it simply protects the yield against insect damage. Without pests, there is no difference in the amount of corn produced, compared to the same variety without Bt. However, Bt is often placed in "elite" hybrids, and these may or may not yield more than older hybrids. (See B-6090, "Bt Corn Technology in Texas: A Practical View," Texas Cooperative Extension.)

 

Subject to EPA approval, transgenic corn for corn rootworm control will be marketed in 2002. While there are several types of rootworm toxins under development, most depend on proteins from Bacillus thuringiensis.  However, these toxins are different from those that are active against caterpillar pests. Rootworm‑active corn will not harm corn borers, and corn borer‑active corn will not harm rootworms. Putting toxins from both rootworm‑active and lepidoptera‑active corn together in the same plant is possible, as is putting two different toxins for rootworms or lepidoptera alone. These would be "stacked gene" hybrids, which will be sold in the future.

 

 

Pre-Emergence Insect Control

Soil-Inhabiting Pests

White grubs, corn rootworms, cutworms, wireworms, sod webworms, seedcorn beetles and seedcorn maggots are the most common soil insects attacking corn in Texas. Cultural practices are very important in reducing damage by these soil pests. Growing corn on the same land year after year increases damage by certain soil insects. For example, losses from corn rootworms may be reduced or in some cases eliminated by rotating corn with soybeans or other crops that are not attacked by rootworms. In most areas of Texas, corn has been rotated successfully with sorghum without damage from the Mexican corn rootworm and western corn rootworm. However, in parts of South Central Texas, corn following sorghum has been damaged by the Mexican corn rootworm, although this is a rare occurrence. Another cultural practice that reduces soil insect pests is to maintain weed‑free fields throughout the year, because weeds are host plants for certain soil insects.

Producers should sample their fields for white grubs, cutworms and wireworms before bed formation. If chemical treatment is necessary, soil or seed treatments are available. One method may be more effective for a particular soil pest than another.

 

Seed Treatment


In the past, seed treatment was done by the seed companies; however, because of restrictions on chemical use on seeds, many commercial seed companies are no longer treating seeds. If commercially treated seeds are not available, growers can use direct seed treatment or planter box treatments.

Light populations of wireworms, seedcorn maggots, seedcorn beetles, and seed‑feeding ants may be effectively controlled by treating seeds with products containing lindane or lindane plus diazinon. When treating the seeds, the insecticide should coat each seed evenly. Use a concrete mixer, commercial seed treater,  or homemade seed treater to treat seeds. Sprinkle 1 pint of water on each 100 pounds of seed and mix this to coat the seed with moisture. Slowly add the correct amount of insecticide while mixing the seed, and mix thoroughly until the insecticide is evenly distributed on all seeds. Treated seeds should be planted within 20 days of treatment, because long exposure to the chemical will affect germination in some hybrids. Do not use treated seed for human consumption or livestock feed.              

 

Some insecticides are made to be applied to seed in the planter box. This method is effective only against low populations of wireworms, seed‑feeding ants, seedcorn beetles and seedworm maggots. Use this soil insect control technique as directed on the insecticide label.

 

Insecticides such as malathion, pirimophosmethyl (Actellic7) or methoxychlor are often applied to seed to control stored grain pests. These insecticides are not effective for control of soil pests.

 

Soil Treatment

Insecticide directed against some soil pests must be applied before the crop is planted or at planting time. Granular or liquid formulations may be used. The formulation used usually depends on the producer=s equipment and the target insect. Granular forms of insecticide are generally safer . With the soil treatment method there are three application techniques: (1) the preplant broadcast, (2) row band or T‑band, and (3) in‑furrow at planting.

 

Preplant Insecticide Application: A broadcast application generally provides the best protection against soil insects and is the only means of controlling heavy white grub infestations. Unfortunately, the broadcast applications require more insecticide and are more expensive than row band or in‑furrow treatments . Therefore, broadcast applications are usually not recommended. However, when broadcast applications are necessary, the insecticide should be applied uniformly to the field and incorporated to a depth of 3 to 5 inches immediately after application. Because of label changes in recent years, fewer products are labeled for preplant broadcast application.

 

When corn is planted on a bed, special equipment is required to incorporate the insecticide to a depth of 3 to 5 inches. This is called row treatment. Row treatments must be made during or after bed formation. Further cultivation or bed shaping will alter the position of the insecticide in the row. A treated band of soil 7 to 10 inches wide and 3 to 5 inches deep, with seed placed in the center of the treated band, is necessary to obtain the best control.

 

Insecticide Application at Planting: Insecticides may be applied to the soil at planting time by the row band, T‑band, or in‑furrow techniques. The technique of choice will depend on the pest insect and how a particular insecticide is labeled. Some insecticides applied at planting for corn rootworm control will suppress some early season pests such as chinch bugs, fire ants and flea beetles on seedling plants. These pests will be suppressed for 2 to 4 weeks depending upon the insecticide used.

 

Mount granular application equipment on the planter with the spout just behind the opening plow or disc opener and in front of the covering shovels or press wheel. Adjust the spouts so that the treatment band is about 6 to 8 inches wide and so that the seed furrow and covering soil are treated. Incorporation of the insecticide by covering shovels is adequate. Insecticide also can be incorporated with short parallel chains, loop chains, press wheels, finger tines or other suitable devices. Some insecticides are labeled only for band application behind the seed covering devices. Do not apply insecticide directly on the seed unless this use is specifically listed on the label, since doing so usually results in poor seed germination. Poor control usually results from in‑furrow application where white grub populations are high.

 

White Grubs and Cutworms

White grubs are the larval stage of May and June beetles. Damage results from larvae feeding on the plant roots. Small damaged plants often are killed and large plants are stunted and may lodge prior to harvest. To determine the need for white grub control before planting, examine a 1‑square‑foot soil sample for each 5 to 10 acres. An average of one white grub per square foot is enough to cause significant stand loss.

 

If white grub populations average approximately one per square foot, adequate suppression can often be achieved with a planting time in‑furrow or band treatment. For surface cutworms, incorporation of insecticide into the top 1 to 2 inches of soil is best. Refer to the table in this document for cutworm control on seedling corn. 

 


SUGGESTED INSECTICIDES FOR CONTROLLING WHITE GRUBS

Insecticides

(listed alphabetically)

Amount per 1,000 feet of row

Amount per acre on 40‑inch row spacing

Chlorpyrifos

(Lorsban7 15G)

 

8.0 oz

6.5 lb

Tebupirimfos + cyfluthrin

(Aztec7 2.1G)

 

6.7 oz

5.5 lb

Tefluthrin

(Force7 3G)

4 ‑ 5 oz

3.3 B 4.1 lb

Terbufos

(Counter7 20CR)

(Counter7 15G)

6.0 oz

8.0 oz

4.9 lb

6.5 lb

 

 

Remarks:

Chlorpyrifos: Not labeled for band application. Must be in‑furrow or T‑band.

 

Tebupirimfos + cyfluthrin: May not be used in counties adjacent to the Gulf Coast. For applications made within 20 yards of aquatic sites, apply as an in‑furrow application only. See Special Local Needs Registration TX‑00008. For optimum results, apply as a band or T‑band. In‑furrow application may provide less control.

 

Tefluthrin: Apply as an in‑furrow treatment.

 

Terbufos: Read supplemental label for information on potential crop damage if used in combination with some herbicides. Banded or in‑furrow application only.

 


Wireworms, Seedcorn Maggots and Seedcorn Beetles

Seed treatment with products containing lindane or lindane plus diazinon is generally effective in controlling these soil pests. See the section seed treatment procedures  for more information. Where large populations of wireworms are present, follow the recommendations listed on appropriate insecticide labels. Producers should check their soil closely during land preparation to determine the need for seed treatment or soil applications to control such pests. 

 

 

 


SUGGESTED INSECTICIDES FOR CONTROLLING WIREWORMS

Insecticides

(listed alphabetically)

Amount per 1,000 feet of row

 

Amount per acre on 40‑inch row spacing

Chlorpyrifos

(Lorsban7 15G)

8.0 oz

6.5 lb

Fipronil

(Regent7 80WG)

0.149 oz

1.95 oz

Tebupirimfos + cyfluthrin

(Aztec7 2.1G)

6.7 oz

5.5 lb

Tefluthrin

(Force7 3G)

4 B 5 oz

3.3 B 4.1 lb

Terbufos

(Counter7 20CR)

(Counter7 15G)

6.0 oz

8.0 oz

4.9 lb

6.5 lb

 

 

Remarks:

Chlorpyrifos: Not labeled for band application. Must be in‑furrow or T‑band.

 

Fipronil: Do not apply on row spacing less than 30 inches. Do not harvest within 90 days of application. Do not plant small grains or other rotational crops within 12 months of application, or root crops within 5 months of application.

 

Tebupirimfos + cyfluthrin: May not be used in counties adjacent to the Gulf Coast. For applications made within 20 yards of aquatic sites, apply as an in‑furrow application only. See Special Local Needs Registration TX‑00008.

 

Tefluthrin: Apply as an in‑furrow treatment.

 

Terbufos: Read supplemental label for information on potential crop damage if used in combination with some herbicides.

 


Mexican and Western Corn Rootworm

Mexican and western corn rootworm beetles lay eggs in the soil during the summer and fall, shortly after silking time. Eggs are usually laid within the corn field in the upper 2 to 8 inches of the soil, where they remain until they hatch the following year. Time of hatching depends to some extent on soil temperature; however, eggs usually begin to hatch about mid‑April in South Texas and about mid‑May in the High Plains and continue to hatch for several weeks. If corn roots are not available for the newly hatched corn rootworms to feed on, they will die. There is only one generation per year; therefore, the best method of controlling these two subspecies is to rotate corn with any other crop.

 

Fields planted to corn year after year in Mexican and western corn rootworm problem areas (see map ) generally require a soil insecticide at planting time. In continuous corn production fields, an average of one or more beetles per plant on any sampling date during the growing season indicates a need for a soil insecticide the following spring or a need to consider crop rotation. Damage from corn rootworms usually occurs from mid‑April through mid‑May in South Texas and during June in the High Plains. Extensive damage to the brace roots and fibrous roots may cause plants to lodge. A "goose necking" appearance occurs when lodged plants continue to grow.

 

 


SUGGESTED INSECTICIDES FOR CONTROLLING MEXICAN

AND WESTERN CORN ROOTWORMS

Insecticides

(listed alphabetically)

Amount per 1,000

feet of row

Amount per acre on 40‑inch row spacing

Carbofuran

(Furadan7 4F)

 

See remarks

2.5 oz

See remarks

1 qt

Chlorpyrifos

(Lorsban7 15G)

(Lorsban7 4E)

8.0 oz

2.4 oz

6.5 lb

2 pt

Tebupirimfos + cyfluthrin

(Aztec7 2.1G)

6.7 oz

5.5 lb

Tefluthrin

(Force7 3G)

4.0 B 5.0 oz

3.3 B 4.1 lb

Terbufos

(Counter7 20CR)

(Counter7 15G)

6.0 oz

8.0 oz

4.9 lb

6.5 lb

 

Remarks:

Carbofuran: Apply as a post emergent spray by banding over the row, or by side dressing or basal spraying both sides of the row after corn emerges. Control will generally be improved if the treatment is incorporated into the soil. Do not feed forage within 30 days of last application.

 

Chlorpyrifos: Granules are not labeled for band application. Must be in‑furrow or T‑band. Liquid formulation must be applied by T‑band application only. Applications made using a band width less than 5 ‑ 6 inches may result in phytotoxicity under certain environmental conditions (e.g., cool temperatures, wet conditions, and light soils).

 

Tebupirimfos + cyfluthrin: May not be used in counties adjacent to the Gulf Coast. For applications made within 20 yards of aquatic sites, apply as an in‑furrow application only.

 

Terbufos: Read supplemental label for information on potential crop damage if used in combination with some herbicides.

 

PRECAUTION: Certain sulfonylurea herbicides and organophosphate insecticides used in the same crop year on corn may result in severe crop injury. Please read pesticide labels carefully. IMPORTANT: The use of the same soil insecticides year after year in the same field is not a good practice. Producers are encouraged to rotate organophosphate (chlorpyrifos, terbufos, tebupirimfos) with other (tefluthrin, cyfluthrin, carbofuran) soil insecticides each year for best results. For all band applications, apply in a 6‑ to 8‑inch band just behind seed drop and in front of covering shovels and press wheel or chain drag. Soil incorporation to a depth of about 1 inch is important.

 

 


Southern Corn Rootworm

 

The southern corn rootworm deposits eggs in soil after the corn is in the seedling stage. Therefore, crop rotation will not provide adequate control of this insect. Unlike the Mexican and western corn rootworms, more than one generation of southern corn rootworm may occur per year. This species is considered a minor corn pest in most areas of Texas where corn is planted in fields that were not grassy or weedy the previous year.

 

In the Gulf Coast region (see map ) however, the southern corn rootworm has been a pest of significance. Where there is a history of infestations along with losses in plant stands in previous years, an in‑furrow or band pesticide application should be considered.

 

With insecticides that can be applied in‑furrow, field experiments show that in most fields one‑half the maximum rate listed in the following table provides the most favorable economic returns for control of southern corn rootworm. However, in fields where heavy infestations occur each year it would be advisable to use the higher rates.

 

 


SUGGESTED INSECTICIDES APPLIED AT PLANTING FOR CONTROLLING SOUTHERN CORN ROOTWORM

Insecticides

(listed alphabetically)

 

Amount per 1,000 feet of row

Amount per acre on

40‑inch row spacing

 

Carbofuran

(Furadan7 4F)

2.5 oz

1 qt

Chlorpyrifos

(Lorsban7 15G)

8.0 oz

6.5 lb

Tefluthrin

(Force7 3G)

4 B 5 oz

3.3 B 4.1 lb

Terbufos

(Counter7 20CR)

(Counter7 15G)

 

6.0 oz

8.0 oz

4.9 lb

6.5 lb

 

Remarks

Carbofuran: Apply at planting directly into the seed furrow. Do not feed forage within 30 days of last application

Terbufos: Read supplemental label for information on potential crop damage if used in combination with some herbicides.PRECAUTION: Certain sulfonylurea herbicides and organophosphate insecticides used in the same crop year on corn may result in severe crop injury. Please read pesticide labels carefully. IMPORTANT: The use of the same soil insecticide year after year in the same field is not a good practice. Producers are encouraged to rotate organophosphate (chlorpyrifos, terbufos) with other (tefluthrin, carbofuran) soil insecticides each year.For all band applications, apply in a 6‑ to 8‑inch band just behind seed drop and in front of covering shovels and press wheel or chain drag. Soil incorporation to a depth of about 1 inch is important.

 


Seedling to Tassel Stage Insect Control

Corn Leaf Aphid

Fields in the seedling stage rarely require treatment for corn leaf aphid. Yield losses have occurred only where corn leaf aphids caused stand loss to seedling plants. Pre‑tassel and later growth stages can tolerate large numbers of aphids without economic damage.

 

Soil Cutworms

Cutworms are dingy, grayish‑black, smooth "worms" that are the larval stages of several different moths. Cutworms are active at night and damage seedling corn by cutting the stalk just above ground level. Large numbers of cutworms may be found in grassy or weedy areas. Most cutworm species hide in the soil during the day and are not visible on the plants.

 

When cutworms are damaging plant stands, an application of insecticide by air or ground usually will give adequate control. Best results are obtained when insecticides are applied in the late afternoon. If the soil is dry, cloddy or crusty at the time of treatment, control may not be as effective as in moist soil.

 


SUGGESTED INSECTICIDES FOR CONTROLLING CUTWORMS

Insecticides

(listed alphabetically)
Amount per acre

Days from last application to:

 

 

Harvest

Grazing

Chlorpyrifos

(Lorsban7 4E)

1 B 2 pt

35

14

Esfenvalerate

(Asana7 XL 0.66E)

5.8 B 9.6 oz

21

21

Permethrin

(Ambush7 2E)

(Pounce7 3.2EC)

(Pounce7 1.5G)

6.4 B 12.8 oz

4.0 B 8.0 oz

6.7 B 13.3 lbs

30

30

30